Service difficulty report · Nut · Bell 407

Difficulty date
January 20, 2012
Submitted
September 14, 2015
Operation
General aviation
Make and model
Bell 407
Aircraft time
3,078 hours
Engine
Allsn 250C47B
Part
Nut
Part number
204040131001
Condition
Worn
Location
M/R Transmission
Stage of operation
NR
How discovered
9
Nature of condition
O
Precautionary procedure
O

As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.

What was found

(CAN) DURING O/H OF THE MAIN TRANSMISSION ASSY DUE TO A CHIP LIGHT IN THE COCKPIT, IT WAS FOUND THAT 3 OF THE NUTS, PN 204-040-131-001 RETAINING BEARING RACE, PN 204-040-130-005 HAD 0 FT/LBS OF TORQUE. THE OTHER 2 NUTS HAD TORQUES OF 25 FT/LBS. OEM TORQUE SPECIFICATIONS FOR THESE NUTS IS BETWEEN 60-80 FT/LBS. DUE TO THE LACK OF TORQUE ON THE NUTS, DAMAGE OCCURRED TO THE SURFACE OF THE NUT IN CONTACT WITH CARRIER ASSY PN 400-040-070-101 AS WELL AS DAMAGE TO BEARING RACE CONTACT AREAS ON THE CARRIER. BASED UPON AN EXAMINATION OF THE TECHNICAL RECORDS OF THE TRANSMISSION, IT IS BELIEVED THAT THE CARRIER ASSY THAT HOUSES THE AFFECTED NUTS HAD NOT BEEN PREVIOUSLY DISASSEMBLED SINCE LEAVING THE OEM FACILITY WHEN NEW.

More about the Bell 407